Approximately 30,000,000 Americans have gallstones. This laboratory's long-term goal has been the evaluation of pathogenic mechanisms which may lead to new strategies to prevent cholesterol gallstones. The major pathogenic factors include 1) cholesterol supersaturated bile, 2) Diminished gallbladder motility, and 3) nucleation and growth of cholesterol monohydrate crystals. In recent years a number of pronucleating agents have been identified, but none account for the majority of whole bile pronucleating activity. Ongoing studies from this laboratory suggest that an 84 kDa nonmucin glycoprotein, which has recently been identified to be transferrin, may play an important role in e cholesterol crystal nucleation process. These observations along with the knowledge that cholesterol gallstones develop most commonly in women of childbearing age have led us to propose a new Central Hypothesis: Iron deficiency results in increased serum and biliary transferrin. increased biliary cholesterol secretion. enhanced cholesterol monohydrate crystal precipitation and cholesterol gallstone formation. Transferrin is a pro-nucleating agent, is concentrated in the vesicular fraction of bile, and is present, as is iron, in higher concentrations in the gallbladder bile of cholesterol gallstone than in control patients. However, the exact type and role of transferrin, and iron, in bile and the possible relationship between iron deficiency and gallstone formation need to be carefully examined. Therefore, we plan to pursue the following aims. The First Specific Aim is to further define the role of transferrin as a pronucleating agent and the relationship between serum and biliary transferrin. The Second Specific Aim is to determine the role of iron in gallstone pathogenesis. The Third Specific Aim is to compare levels of transferrin, iron, transferrin receptors, and hepatic enzymes in controls as well as cholesterol gallstone patient and animals. The Fourth Specific Aim is to determine the presence and site of transferrin and iron in cholesterol gallstones. The Fifth Specific Aim is to define the relationship between iron deficiency, biliary transferrin, an cholesterol gallstone formation. A series of human and prairie dog studies should confirm the proposed link between iron deficiency, biliary transferrin and cholesterol gallstones.